Dicarboxylic sulfones as plasticizers for vinyl chloride polymers



United States Patent O DICARBOXYLIC SULFONES AS PLASTICIZERS FOR VINYLCHLORIDE PQLYMERS William S. Emerson and Robert A. Heimsch, Dayton,Ohio, assignors to Monsanto Chemical Company, St. Lo i M a poration ofDelawar N0 Dr n O n l pp i o p 2 H fieriat No. 157,182, now Patent No.2,689,364, dated September 21, 1954. Divided and this application March17, 1954, Serial No. 416,957

Claims. (Cl. 26030.8)

Q-cmsmcmcooa ROOC in which R is a member of the group consisting ofhydrogen and alkyl groups of from 1 to 8 carbon atoms. As illustrativeof compounds having the above general structure may be mentioned 2-, 3-,or 4-carboxybenzyl carboxymethyl sulfone, 4-carbomethoxybenzylcarbornethoxyniethyl sulfone, 3-carboisopropoxybenzyl carboethoxymethylsulfone, Z-carbobutoxybepzyl carbobutoxymethyl sulfo e, rbo(2- thyl y xyzy n methyl sulfone and 3-carbooctyloxybenzyl octyloxymethyl sulfone.

The. present new dicarboxy sulfones or their dialkyl esters are readilyobtainable by oxidation of carboxybenzyl carboxymethyl sulfides ormonoor di-alkyl esters of the same, Oxidation of the sulfides to thecorresponding sulfones may be effected by contacting with a mildoxidizing agent, e. g., an organic or inorganic oxygenliberating agentsuch as hydrogen peroxide, barium peroxide, benzoyl peroxide, potassiumpersulfate, etc. For ease in manipulation, hydrogen peroxide ispreferred. The oxidation is preferably eifected in an unreactive solventmedium such as glacial acetic acid, acetone, methyl ethyl ketone, etc.Depending upon the nature of the reactants, as well as upon the rate atwhich the oxidizing agent is added to the sulfide, various temperaturesmay be employed for the oxidation. Cooling is often necessary with themore active peroxides; in other cases ordinary or even increasedtemperatures may be emp oy Dialkyl esters of the carboxybenzylcarboxymethyl sulfones are also obtainable by esterifying the free acidswith an unsubstituted, aliphatic saturated alcohol of from 1 to 8 carbonatoms, preferably in the presence of an esterifying catalyst. The higheralkyl esters, i. e., carboalkoxybenzyl carboalkoxymethyl sulfones, inwhich the alk oxy group has from 4 to 8 carbon atoms, are moreadvantageously prepared; however, by an interchange reaction whereby alower dialkyl ester of a carboxybenzyl carboxymethyl sulfone, -forexample, the dimethyl ester is reacted with an unsubstituted, aliphaticsaturated alcohol of from 4 to 8 carbon atoms in the presence of anesterifying catalyst.

Catalysts of general utility in both types of esteriiications are acidicmaterials, for example, p-toluenesulfonic acid, sulfuric acid,pyrophosphoric acid, hydrochloric acid, etc. In both esterifyingprocedures, formation of the desired esters o'ccugsto some extent at;ordinary room emperature; how ve ino deritoobtain go d y d We pte e -tope e atre'flux ng emp a u s h e removing from the reaction zone, eitherthe water which is given temperatures.

off during the direct esterification or the lower alcohol generated inthe interchange reaction.

The carboxybenzyl carboxymethyl sulfones and their lower alkyl estersare stable, crystalline solids or viscous, high-boiling liquids, whichmay be advantageously employed in the chemical and allied industries fora wide variety of purposes. The free acids, i. e., the 2-, 3- and4-car'ooxybenzyl carboxymethyl sulfones may serve as intermediates inthe production of synthetic fibers of the dicarboxylamide type, and inthe production of non-ionic Wetting-out and detersive agents.

Dialkyl esters of the carboxybenzyl carboxymethyl sultones in which thealkyl groups have from 4 to 8 carbon atoms are highly efficientplasticizers for vinyl chloride polymers. A wide variety of plasticizershas been employed for the purpose of improving the physical propertiesof vinyl chloride polymers. Particular attention has been given to theimprovement of flexibility and heat and light stability of suchplasticized compositions. In many instances the improvement inflexibility has been obtainable only by sacrificing other desirableproperties of an ideal polyvinyl chloride composition, such as lowvolatility, color and heat stability, water absorption, etc. We havefound that very good flexibility, without sacrifice of temperaturestability and low volatility, is imparted to vinyl chloride polymerswhere the present esters are employed as plasticizers for such polymers.

The present esters are valuable plasticizers for polyvinyl chloride andcopolymers of at least 70 per cent by weight of vinyl chloride and up to30 per cent by weight of an unsaturated monomer copolymerized therewith,for example, vinyl acetate, vinylidene chloride, etc.

We have found these esters serve not only to soften vinyl chloridepolymers, but also to impart simultaneously a high degree of lowtemperature flexibility, very good temperature stability and greatmechanical strength to these polymers. The present esters are compatiblewith vinyl chloride polymers and show no exudation of plasticizer evenat plasticizer contents of up to 50 per cent. Although the quantity ofplasticizer will depend upon the particular polymer to be plasticizedand upon its molecular weight, it is generally found that compositionshaving from 5 per cent to 50 per cent by weight of plasticizer will, inmost cases, be satisfactory for general utility. The good flexibility ofthe plasticized compositions increases with increasing plasticizerconcentration.

In evaluating plasticizer efficiency use is made of the followingempirical testing procedures:

Compatibility.-Visual inspection of the plasticized composition isemployed, incompatibility of the plasticizer with the polymer beingdemonstrated by cloudiness and exudation of the plasticizer.

Hardness-A standard instrument made by the Shore Instrument Company isused for this determination and expresses the hardness in units from 1to 100. The hardness of a composition is judged by its resistance to thepenetration of a standard needle applied to the composition under astandard load for a standard, length of time.

Low temperature flexibility-Low temperature flexibility is one of themost important properties of elastomeric vinyl compositions. willproduce flexible compositions at room temperature the flexibility ofthese compositions at low temperatures, may vary considerably, i. e.,plasticized polyvinyl chloride compositions that are flexible at roomtemperature often become very brittle and useless at low tempera Lowtemperature flexibility tests herein employed tures. are according tothe Clash-Berg method. This method determines the torsional flexibilityof a plastic atvarious While many plasticizers The temperature at whichthe vinyl chlo-j ride composition exhibits an arbitrarily establishedminimum flexibility is defined as the low temperature flexibility of thecomposition. This value may also be defined as the lower temperaturelimit of the plasticized compositions usefulness as an elastomer.

Vlatility.]ust as a decrease in low temperature often results indecreased flexibility of a plasticized polymer composition so does adecrease in plasticizer concentration when caused by volatilization ofthe plasticizer. Hence, plasticizers which are readily volatilized fromthe plasticized composition as a result of aging or heating areinefficient because upon volatilization the plasticized compositionsbecome still and hard. The test for plasticizer volatility hereinemployed is that described by the American Society for Testing Materialsunder the designation D-744-44T.

Water resistance.-The amount of water absorption and the amount ofleaching that takes place when the plasticized composition is immersedin distilled water for 24 hours is determined.

The invention is further illustrated but not limited by the followingexamples:

Example 1 To 145 g. of 4-carbomethoxybenzyl carbomethoxymethyl sulfide(obtained by reacting 4-(chloromethyl)- benzoyl chloride withthioglycolic acid and esterifying the resulting 4-carboxybenzylcarboxymethyl sulfide with methanol) and 500 cc. of glacial acetic acidthere was added 20 cc. of 30% hydrogen peroxide during a time of 10minutes, the temperature rising from 25 C. to 54 C. during the addition.An additional 180 cc. of hydrogen peroxide was then added over a 40minute period. The maximum temperature of the reaction mixture duringthe addition was observed to be 80 C. Within 10 minutes the temperatureof the reaction mixture rose to 105 C. Within another 10 minutes it haddropped to 90 C. and was held at this temperature for another 45minutes. Addition of 1000 cc. of water to the mixture and subsequentcooling resulted in some crystallization. Filtration of the crystalsformed and repeated crystallization of the filtrate gave 5 crops ofcrystals which upon recrystallization from methanol gave 163 g. (81.7%theoretical yield) of 4-carbomethoxybenzyl carbomethoxymethyl sulfone,M. P. 1045-105 C., and analyzing as follows:

Calcd. for CHHHOBS Found Percent C 50. 35 50. 44 Percent H 4. 89 4. 6S

4-carbomethoxybenzyl carbomethoxymethyl sulfone may be readilyhydrolyzed to the free acid, 4-carboxybenzyl carboxymethyl sulfone.

Example 2 sulfonic acid was placed in a flask fitted with a 24" Vigreauxcolumn and refluxed for 10 hours under slightly reduced pressure withthe pot temperature being from 145 to 155 C. During the refluxing,methanol was removed as it was formed. The reaction mixture was thenwashed with a 5% aqueous solution of sodium bicarbonate and ether wasadded to break the resulting emulsion. The whole was then washed withwater until neutral, 10 g. of charcoal (Norite) was added, and the etherand unreacted 2-ethylhexanol (23 g.) were distilled off. The residue wasthen heated to a temperature of 165 C./ 0.25 mm. in order to drive ofilow-boiling materials and held at a temperature of from to C./0.25 mm.for 1.5 hours. Filtration of the product to remove the charcoal gave 56g. (89.8 per cent yield) of 4-carbo (2-ethylhexyl oxybenzyl carbo(2-ethylhexyl) oxymethyl sulfone, molecular refraction 132.47 (calcd.134.40), and analyzing as follows:

The reaction of other alcohols of from 4 to 8 carbon atoms, instead ofZ-ethylhexanol, with 4-carbomethoxybenzyl carbomethoxymethyl sulfone maybe effected similarly, as with n-hexanol and the dimethyl ester to yield4-carbo-n-hexoxybenzyl carbo-n-hexoxymethyl sulfone, or with isobutanoland 4-carbornethoxybenzyl carbornethoxymethyl sulfone to yield4-carbo-isobutoxybenzyl carbo-isobutoxymethyl sulfone, etc. When workingwith the higher alcohols, the diethyl ester, instead of the dimethylester, may be used for the interchange reaction. Also, instead of usingthe 4-isomers, the 2- or 3-isomer may be employed, i. e., the methyl orethyl esters of 2- or 3-carboxybenzyl carboxymethyl sulfone may beemployed to yield the higher dialkyl ester of 2- or 3-carboxybenzylcarboxymethyl sulfone.

Example 3 Sixty parts of polyvinyl chloride and 40 parts by weight of4-carbo(2-ethylhexyl)oxybenzyl carbo(2-ethylhexyl)oxymethyl sulfone aremixed on a rolling mill to a homogeneous blend. During the milling therewas observed substantially no fuming and discoloration. A molded sheetof the mixture was clear and transparent and substantially colorless.Testing of the molded sheet for low temperature flexibility, accordingto the testing procedure described above, gave a value of minus 13 C.Tests on the volatility characteristics of the plasticized compositiongave a value of 0.9 per cent, which showed very good retention ofplasticizer and indicated good temperature characteristics of thecomposition. The plasticized material had a hardness of 82 before thevolatility test and a hardness of 79 after the volatility test. Whensubjected to heat at a temperature of 325 F. for a period of 30 minutesthe clarity and color of the molded product were substantiallyunchanged. Tests of the waterresistance properties of the plasticizedmaterial employing the test procedure described above showed asolids-loss of only 0.03 per cent and an 0.36 per cent water absorptionvalue.

Instead of the esters employed in the examples above, other esters ofcarboxybenzyl carboxymethyl sulfones may be used to give similarlyvaluable plasticized polyvinyl chloride compositions. Thus, by employing40 parts by weight of di-n-octyl, di-isoamyl, di-n-hexyl or dibutylesters of 2-, 3- or 4- carboxybenzyl carboxymethyl sulfone with 60 partsby weight of polyvinyl chloride or with 60 parts by weight of a vinylchloride-vinyl acetate copolyrner known to the trade as Vinylite, orVYNW, there may be obtained clear, colorless compositions of very goodflexibility and stability.

While the above examples show only a composition in which the ratio ofplasticizer to polymer content is 40:60, this ratio being employed inorder to get comparable efficiencies, the content of ester to polyvinylchloride may be widely varied, depending upon the properties desired inthe final product. For many purposes a plasticizer content of, say, fromonly 10 per cent to 20 per cent is preferred. The present esters arecompatible with polyvinyl chloride over a wide range of concentrations.

Although the invention has been described particularly with reference tothe use of the present carboalkoxybenzyl carboalkoxymethyl sulfones asplasticizers for erties of the present esters.

polyvinyl chloride, these esters may be advantageously employed also asplasticizers for copolymers of vinyl chloride, for example, thecopolymers of vinyl chloride with vinyl acetate, vinylidene chloride,methyl methacrylate, acrylonitrile, or styrene. Preferably, suchcopolymers have a high vinyl chloride content, i. e., a vinyl chloridecontent of at least 70 per cent by weight of vinyl chloride and up to 30per cent by weight of the the copolymerizable monomer.

The plasticized polyvinyl halide compositions of the present inventionhave good thermal stability; however, for many purposes it may beadvantageous to use known stabilizers in the plasticized compositions.Inasmuch as the present esters are substantially unreactive with thecommercially available heat and light stabilizers which are commonlyemployed with polyvinyl chloride or copolymers thereof, the presence ofsuch additives in the plasticized materials does not impair the valuableprop- The present esters are of general utility in softening vinylchloride polymers. They may be used as the only plasticizing componentin a compounded vinyl chloride polymer or they may be used inconjunction with other plasticizers.

This application is a division of our copending application Serial No.157,182, filed April 20, 1950, now U. S. Patent No. 2,689,864, issuedSeptember 21, 1954.

We claim:

1. A resinous composition comprising polyvinyl chloride plasticized witha carboalkoxybenzyl carboalkoxymethyl sulfone in which each alkoxy grouphas from 4 to 8 carbon atoms.

2. A resinous composition comprising polyvinyl chloride plasticized witha carboalkoxybenzyl carboalkoxymethyl sulfone in which each alkoxy grouphas from 4 to 8 carbon atoms, said sulfone being from five to 50 percent of the weight of the composition.

3. A resinous composition comprising a polymer of at least 70 per centby weight of vinyl chloride and up to per cent by weight of anunsaturated monomer copolymerizable therewith, said copolymer beingplasticized with a carboalkoxybenzyl carboalkoxymethyl sulfone in whicheach alkoxy group has from 4 to 8 carbon atoms.

4. A resinous composition comprising a copolymer of at least 70 per centby weight of vinyl chloride and up to 30 per cent by weight of anunsaturated monomer copolymerizable therewith, said copolymer beingplasticized with a carboalkoxybenzyl carboalkoxymethyl sulfone in whicheach alkoxy group has from 4 to 8 carbon atoms, and said sulfone beingfrom 5 to per cent of the weight of the composition.

5. A resinous composition comprising polyvinyl chloride plasticized with4-carbo(2-ethylhexyl)oxybenzyl carbo(2-ethylhexyl)oxymethyl sulfone,said sulfone being from five to 50 per cent of the weight of thecomposition.

No references cited.

3. A RESINOUS COMPOSITION COMPRISING A POLYMER OF AT LEAST 70 PER CENTBY WEIGHT OF VINYL CHLORIDE AND UP TO 30 PER CENT BY WEIGHT OF ANUNSATURATED MONOMER COPOLYMERIZABLE THEREWITH, SAID COPOLYMER BEINGPLASTICIZED WITH A CARBOALKOXYBENZYL CARBOALKOXYMETHYL SULFONE IN WHICHEACH ALKOXY GROUP HAS FROM 4 TO 8 CARBON ATOMS.